1. Field of the Invention
The present invention relates to exposure apparatuses, in which a pattern of an original plate is projected on a substrate, for use in a semiconductor manufacturing process, and in particular relates to a lithography machine using EUV light (extreme ultraviolet light) as exposure light.
2. Description of the Related Art
An example in the related art is shown in FIGS. 5 and 6. A pumping laser 101, such as a YAG (yttrium aluminum garnet) solid laser, irradiates with the laser a luminescent point of a light source where a light source material is evaporated, condensed, or atomized so as to make the light source material radiate by plasma excitation.
A luminescent light source unit 102 has a structure maintained under vacuum. A light source 102A is a luminescent point of exposure light.
A vacuum chamber 103 accommodates the entire exposure apparatus, and is maintained to form a vacuum by a vacuum pump 104.
An exposure light entry site 105 leads the exposure light from the luminescent light source unit 102, and is composed of mirrors A to D denoted by 105A to 105D, respectively, so as to homogenize and shape the exposure light.
On a moving part of a reticle stage 106, a reflection original plate 106A having a pattern to be transcribed on a substrate is mounted.
A mirror optical system 107 projects the pattern of the original plate 106A so as to reduce it. That is, the light reflected from the original plate 106A is sequentially reflected by mirrors A to E denoted by 107A to 107E, respectively, so as to form the pattern of the original plate on a substrate with a predetermined demagnification factor.
A wafer 108A, which is a Si substrate having the pattern on the original plate 106A projected thereon under demagnification, is mounted on a wafer stage 108 and positioned at a predetermined exposure position. The wafer stage 108 moves with six degrees of freedom, which are translations in X, Y, and Z directions, tilts about the X and Y axes, and a rotation about the Z axis.
A reticle stage support 109 supports the reticle stage 106 on an installation floor.
A projection system support 110 supports the reduced projection mirror optical system 107 on the installation floor.
A wafer stage support 111 supports the wafer stage 108 on the installation floor.
Control units for measuring and controlling relative position (not shown) are provided between the reticle stage 106 and the reduced projection mirror optical system 107 and between the wafer stage 108 and the reduced projection mirror optical system 107, respectively, so as to maintain predetermined relative positions.
The reticle stage support 109, the projection system 110, and the wafer stage support 111 are provided with a mount (not shown) for isolating from the vibration of the installation floor, respectively.
A reticle stocker 112 houses the original plate 106A (reticle) conveyed within the system from outside, and a plurality of the reticles enclosed in a container can be accommodated therein.
A reticle changer 113 selects the reticle to be used from the reticle stocker 112 and conveys it.
A reticle alignment unit 114 includes a rotary hand which can be moved in the X, Y, and Z directions and is rotatable about the Z axis. The original plate 106A received from the reticle changer 113 is rotated by 180° and conveyed to a part of a reticle alignment scope 115 provided at the end of the reticle stage 106 so as to slightly move for alignment relative to an alignment mark 115A provided based on the reduced projection mirror optical system 107.
The aligned original plate 106A is chucked on the reticle stage 106.
A wafer stocker 116 stores the wafer 108A conveyed within the system from outside, and a plurality of the wafers are accommodated.
A wafer conveying robot 117 selects the wafer 108A to be exposed from the wafer stocker 116 so as to convey it to a wafer mechanical pre-alignment air conditioner 118.
In the wafer mechanical pre-alignment air conditioner 118, the rotational position of the wafer about the Z axis is roughly adjusted while the wafer temperature is matched with that of the inside of the air-conditioned exposure apparatus.
A wafer feed hand 119 feeds the wafer 108A aligned and air-conditioned in the wafer mechanical pre-alignment air conditioner 118 to the wafer stage 108.
Gate valves 120 and 121 have gate closing mechanisms for use during conveying the reticle and wafer from outside.
Also, a gate valve 122 opens and closes only when the wafer 108A is conveyed through a barrier between spaces of the wafer stocker 116 and the wafer mechanical pre-alignment air conditioner 118 and the exposure space.
In such a manner, by separating the inside of the system with the barrier, the air volume once vented to the atmosphere when the wafer 108A is conveyed to and from the outside is minimized, enabling rapid return to the vacuum.
In such a conventional exposure apparatus, as shown in FIG. 6, a gas (degassing out resist gas) 108B generated from a resist applied on the wafer 108A during exposure contaminates the vacuum atmosphere so as to produce a stuck contaminant 107F on the respective reflection surfaces of the mirrors A to E of the reduced projection mirror optical system 107. Thereby, the wave aberration of the mirror optical system is deteriorated or the reflectance thereof is reduced, so that the very severe accuracy demanded for the reflecting projection optical system cannot be satisfied.
These as a whole lead to the deterioration of fundamental performances of the exposure apparatus such as exposure accuracies and throughputs.